Nutritional and physiological regulation of glassy-winged sharpshooter oogenesis

Authors: Sisterson, Mark; Brent, Colin

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2021
Publication Date: 1/13/2022
Citation: Sisterson, M.S., Brent, C.S. 2022. Nutritional and physiological regulation of glassy-winged sharpshooter oogenesis. Journal of Economic Entomology. 115(2):526-538. https://doi.org/10.1093/jee/toab260.
DOI: https://doi.org/10.1093/jee/toab260

Interpretive Summary: The glassy-winged sharpshooter is an invasive insect that transmits the plant pathogen, Xylella fastidiosa. Xylella fastidiosa causes numerous plant diseases, including Pierce’s disease of grapevine. Epidemics of Pierce’s disease in southern California were associated with large populations of glassy-winged sharpshooter. Glassy-winged sharpshooter females emerge without mature eggs and an unidentified stimulus is required to initiate egg production. Studies were completed to determine effects of nutritional status on initiation of egg production and to document changes in juvenile hormone and biogenic amine levels associated with egg production. While adult diet affected total number of eggs produced by a female, initiation of egg production was not related to juvenile or adult diet. Reproductively active females had greater juvenile hormone and octopamine levels than reproductively inactive females. However, a topical application of a juvenile hormone analog did not induce egg production. Identification of the stimulus that initiates egg production and description of the regulatory pathways associated with egg production may lead to development of a novel target for suppressing glassy-winged sharpshooter population growth.

Technical Abstract: The glassy-winged sharpshooter (GWSS; Homalodisca vitripennis) is an invasive insect that transmits the plant pathogenic bacterium Xylella fastidiosa. GWSS are polyphagous, with nymphs often moving among plant species during development. Adult females emerge with nascent oocytes and laboratory reared GWSS display a pre-oviposition period of variable duration. While adult feeding is required to gain the resources to produce eggs, the role of nutritional status on initiating oogenesis is poorly understood. To understand effects of GWSS nutrition on nymphal development, oogenesis, and fecundity, GWSS were reared on cowpea, sunflower, sorghum, and a mixture of the three plant species. Adults emerging from cowpea, sunflower, or plant mixture treatments had shorter development times, attained larger size, and had greater residual wet weight (a proxy for lipid reserves) than females reared on sorghum. In choice tests, nymphs avoided sorghum and preferentially fed on cowpea and sunflower. Adult females provisioned with a single plant species during the nymphal stage were provided with either the same host plant species or a mixture of host plant species (cowpea, sunflower, sorghum) for a 9-week oviposition period. During the 9-week oviposition period 37% of adults initiated oogenesis, with ovipositing females having greater juvenile hormone and octopamine levels than reproductively inactive females. While oogenesis was associated with an increase in juvenile hormone level, topical application of the juvenile hormone analog Methoprene did not promote oogenesis. Across nymphal diets, reproductively active females produced more eggs when held on plant mixtures than on single plant species. In choice tests, adult females were observed most frequently on cowpea, although most eggs were deposited on sorghum, the host least preferred by nymphs. Results suggests that fecundity is largely determined by quality of the adult diet, although the stimulus that initiates oogenesis does not appear to be nutrition related.